Endoplasmic reticulum (ER) stress promotes tumor cell escape from immunosurveillance. However, the underlying mechanisms remain unknown. We hypothesized that ER stress induces hepatocellular carcinoma (HCC) cells to release exosomes, which attenuate antitumor immunity by modulating the expression of programmed death ligand 1 (PD‐L1) in macrophages. In this study, we demonstrated that expression of several ER stress markers (glucose‐regulated protein 78, activating transcription factor 6, protein kinase R–like ER kinase, and inositol‐requiring enzyme 1α) was up‐regulated in HCC tissues and negatively correlated with the overall survival and clinicopathological scores in patients with HCC. Expression of ER stress–related proteins positively correlated with CD68⁺ macrophage recruitment and PD‐L1 expression in HCC tissues. High‐throughput sequencing analysis identified miR‐23a‐3p as one of the most abundant microRNAs in exosomes derived from tunicamycin (TM)‐treated HCC cells (Exo‐TMs). miR‐23a‐3p levels in HCC tissues negatively correlated with overall survival. Treatment with Exo‐TMs up‐regulated the expression of PD‐L1 in macrophages in vitro and in vivo. Bioinformatics analysis suggests that miR‐23a‐3p regulates PD‐L1 expression through the phosphatase and tensin homolog (PTEN)–phosphatidylinositol 3‐kinase–protein kinase B (AKT) pathway. This notion was confirmed by in vitro transfection and coculture experiments, which revealed that miR‐23a‐3p inhibited PTEN expression and subsequently elevated phosphorylated AKT and PD‐L1 expression in macrophages. Finally, coculture of T cells with Exo‐TM–stimulated macrophages decreased CD8⁺ T‐cell ratio and interleukin‐2 production but increased T‐cell apoptosis in vitro. Conclusion: ER‐stressed HCC cells release exosomes to up‐regulate PD‐L1 expression in macrophages, which subsequently inhibits T‐cell function through an exosome miR‐23a–PTEN–AKT pathway. Our findings provide insight into the mechanism how tumor cells escape from antitumor immunity.

Ferroptosis, a novel type of programmed cell death, is involved in inflammation and oxidation of various human diseases, including diabetic kidney disease. The present study explored the role of high-mobility group box-1 (HMGB1) on the regulation of ferroptosis in mesangial cells in response to high glucose. Compared with healthy control, levels of serum ferritin, lactate dehydrogenase (LDH), reactive oxygen species (ROS), malonaldehyde (MDA), and HMGB1 were significantly elevated in diabetic nephropathy (DN) patients, accompanied with deregulated ferroptosis-related molecules, including long-chain acyl-CoA synthetase 4 (ACSL4), prostaglandin-endoperoxide synthase 2 (PTGS2), NADPH oxidase 1 (NOX1), and glutathione peroxidase 4 (GPX4). In vitro assay revealed that erastin and high glucose both induced ferroptosis in mesangial cells. Suppression of HMGB1 restored cellular proliferation, prevented ROS and LDH generation, decreased ACSL4, PTGS2, and NOX1, and increased GPX4 levels in mesangial cells. Furthermore, nuclear factor E2-related factor 2 (Nrf2) was decreased in DN patients and high glucose-mediated translocation of HMGB1 in mesangial cells. Knockdown of HMGB1 suppressed high glucose-induced activation of TLR4/NF-κB axis and promoted Nrf2 expression as well as its downstream targets including HO-1, NQO-1, GCLC, and GCLM. Collectively, these findings suggest that HMGB1 regulates glucose-induced ferroptosis via Nrf2 pathway in mesangial cells.

Immunosuppression is a significant factor in the progression of tumor invasion and metastasis. Melatonin, a well-known hormone, has certain cytotoxic and immune regulatory effects to inhibit tumor function. Exosomes are small membrane vesicles released by many kinds of cells, which contain different macromolecules, such as mRNAs and microRNAs (miRNAs), and proteins that can mediate communications between cells. Tumor-derived exosomes may cause immunosuppression, however, it is unknown whether melatonin can attenuate an immunosuppressive status by altering the function of tumor-derived exosomes. In the present study, we evaluated the effects of hepatocellularcarcinoma-derived exosomes (Exo-con) and exosomes derived from hepatocellularcarcinoma cells treated with 0.1 mM melatonin (Exo-MT), on the expression of inflammatory factors and programmed death ligand 1(PD-L1) by co-culturing Exo-con and Exo-MT, respectively, with macrophages differentiated from THP-1 cells or RAW264.7 cells. Our in vitro results indicate that Exo-MT can downregulate the expression of PD-L1 on macrophages while Exo-con can upregulate the expression of PD-L1 through flow cytometry and immunofluorescence analysis. In addition, Exo-con upregulates the secretion of cytokines, such as IL-6, IL-10, IL-1β, and TNF-α in macrophages. Accordingly, Exo-MT could attenuate the high expression of these inflammatory cytokines. Furthermore, in vivo experiments confirmed the results found in vitro. PD-L1 expression and cytokine secretion were lower in the Exo-MT group compared with those in the Exo-con group. Working to identify a specific mechanism, our research shows that Exo-MT decreases STAT3 activation compared to the Exo-con group. In summary, we found exosomes from melatonin treated hepatocellularcarcinoma cells alters the immunosupression status through STAT3 pathway in macrophages. Our study may provide a new avenue to investigate the mechanisms of melatonin in regulating an immunosuppressive status.

Breast cancer is the most commonly occurring cancer and second leading cause of mortality in women. Metformin is a widely prescribed anti-hyperglycemic drug, which is emerging as a potential cancer preventative and treatment agent. However, the mechanisms underlying the suppressive effects of metformin on cancer cell growth and the induction of cancer cell apoptosis are not fully elucidated. The present study aimed to identify the pathways regulated by metformin in two breast cancer cell lines, MDA‑MB‑231 and MDA‑MB‑435. Cells were treated with various concentrations of metformin and then evaluated with respect to viability, proliferation, adenosine triphosphate (ATP) and reactive oxygen species (ROS) levels, mitochondrial membrane potential (∆ψm), and the expression of anti‑ and pro‑apoptotic proteins. Metformin caused apoptosis in a concentration‑ and time‑dependent manner, and decreased cell viability and ATP production. Furthermore, metformin induced the generation of ROS and decreased the ∆ψm. Moreover, metformin downregulated the expression of the anti‑apoptotic proteins B‑cell lymphoma 2 (BCL‑2) and myeloid cell leukemia‑1, and upregulated the expression of the pro‑apoptotic BCL‑2‑associated X protein in MDA‑MB‑231 cells. These results demonstrate that the apoptotic and cytotoxic effects of metformin on breast cancer cells are mediated by the intrinsic mitochondria-mediated apoptosis pathway.

Emerging evidence showed that epigenetic regulation plays important role in the pathogenesis of HCC.N4-acetocytidine (ac4C) was an acetylation chemical modification of mRNA, and NAT10 is reported to regulate ac4C modification and enhance endoplasmic reticulum stress (ERS) in tumor metastasis. Here, we report a novel mechanism by which NAT10-mediated mRNA ac4C-modified HSP90AA1 regulates metastasis and tumor resistance in ERS of HCC. Immunohistochemical, bioinformatics analyses, and in vitro and in vivo experiments, e.g., acRIP-Seq, RNA-Seq, and double luciferase reporter experiment, were employed to investigate the effect of NAT10 on metastasis and drug resistance in HCC. The increased expression of NAT10 was associated with HCC risk and poor prognosis. Cell and animal experiments showed that NAT10 enhanced the metastasis ability and apoptosis resistance of HCC cells in ERS and ERS state. NAT10 could upregulate the modification level of HSP90AA1 mRNA ac4C, maintain the stability of HSP90AA1, and upregulate the expression of HSP90AA1, which further promotes the metastasis of ERS hepatoma cells and the resistance to apoptosis of Lenvatinib. This study proposes a novel mechanism by which NAT10-mediated mRNA ac4C modification regulates tumor metastasis. In addition, we demonstrated the regulatory effect of NAT10-HSP90AA1 on metastasis and drug resistance of ERS in HCC cells.

Exosomes derived from gefitinib-treated EGFR-mutant lung cancer cells alter cisplatin sensitivity via up-regulating autophagy